Page 1 of 2 12 LastLast
Results 1 to 10 of 18

Thread: Bit breaking cutting poplar

  1. #1
    Join Date
    Mar 2011
    Location
    Louisiana
    Posts
    53

    Default Bit breaking cutting poplar

    We are working on a project involving poplar boards and we are having issues with our onsrud 57-910 1/4" downcut bits breaking on multiple occasions. We've talked to onsrud a few times and verified our feeds and speeds according to their chip load calculations and we still are having issues. The last suggestion they had was to purchase a torque wrench to make sure we aren't over-tightening the collet nut but I don't want to spend the money on a torque wrench if it's not necessary. We haven't had this problem with any other material but the poplar, if anyone has suggestions I would really appreciate it.

    Feeds and speeds:

    18,000 RPM
    .75" thick poplar with .25" cutting depth on each pass
    3.4 in/sec


    Thanks

    -P

  2. #2
    Join Date
    Sep 2006
    Location
    cnc routing, portland or
    Posts
    3,633

    Default

    the only thing I see is the rpms are high 8k or so is plenty. I usualy cut at 3ips at that depth in tropical woods so poplar should be fine I would think.

  3. #3
    Join Date
    Jul 2005
    Location
    Brookline, New Hampshire
    Posts
    434

    Default

    Is it practical to blow out the cut between each pass?

    Paul Z

  4. #4
    Join Date
    Oct 2000
    Location
    Atlanta GA
    Posts
    1,499

    Default

    How long has it been since you replaced your collet? A worn out collet is a common cause of broken bits.

    I agree the spindle speed is way too high. I cut solid wood at no more than 12K RPM, often lower.

    Also, are you providing any relief in that kerf for the deeper passes? I find I get better results if I cut the first pass or two in two passes each, with an allowance on one pass, so that I'm routing a wider kerf than the bit. Having the bit follow in it's own footsteps leads to a deep kerf where the bit rubs the walls of the kerf the whole time. Between that and the high RPMs, that could be generating a lot of heat, which is the enemy of router bits.
    Last edited by beacon14; 01-18-2012 at 03:34 PM. Reason: thought of more to say
    David Buchsbaum
    Beacon Custom Woodwork, Inc.
    dba Atlanta Closet & Storage Solutions
    404-309-9146
    david@atlantacloset.com

    atlantacloset.com
    beaconcustomwoodwork.com

  5. #5
    Join Date
    Mar 2004
    Location
    Delray Beach, FL
    Posts
    3,708

    Default

    What model is your machine and spindle?

  6. #6
    Join Date
    Sep 2006
    Location
    cnc routing, portland or
    Posts
    3,633

    Default

    Quote Originally Posted by paul_z View Post
    Is it practical to blow out the cut between each pass?

    Paul Z
    no I mean it would save some bit wear but I have never done it. I rely on sawdust to help hold parts in place.

  7. #7
    Join Date
    Mar 2005
    Location
    Beckwith Decor Products, Derby/Wichita KS
    Posts
    612

    Default

    First thing is what is your chip load size? For the 57-910 is should measure .005-.007. That will tell you if your rpm's are too high or not also what is the temp of the bit? at 18k and a downcut I would expect you're overheating the tool.

    Since your running at 210ipm your rpm should be around 15500-16500 to obtain the correct chipload at that feedrate.

    secondly where is the bit breaking? if its right at the base of the collet then more than likely you have a bad collet.
    Gary
    Beckwith Decor Products
    Caveco Distributor, USA
    Custom CNC Tooling/Onsrud Distributor


  8. #8
    Join Date
    Mar 2011
    Location
    Louisiana
    Posts
    53

    Default

    Our machine is a PRSAlpha with a Columbo spindle. We replaced the collet every time a bit broke inside of the collet. We ran those feeds and speeds by onsrud and shopbot and they said that they were fine. I guess we'll try reducing the spindle speed and see if that yields different results.


    Thanks for your responses,


    -P

  9. #9
    Join Date
    Dec 2007
    Posts
    2,383

    Default

    Have you tried an upcut or straight cutter

  10. #10
    Join Date
    Mar 2011
    Location
    Louisiana
    Posts
    53

    Default

    Yes, upcut broke as well.

Similar Threads

  1. staining poplar?
    By myxpykalix in forum ShopBotter Message Board
    Replies: 9
    Last Post: 03-03-2014, 10:55 AM
  2. Carving poplar
    By myxpykalix in forum ShopBotter Message Board
    Replies: 12
    Last Post: 02-07-2012, 12:05 PM
  3. Cutting 3/4" Poplar Plywood
    By COBOB in forum ShopBot Buddy
    Replies: 10
    Last Post: 08-25-2011, 10:32 PM
  4. Problem cutting 1 inch poplar
    By yobot in forum Archives2008
    Replies: 7
    Last Post: 09-08-2008, 09:43 AM
  5. Help on breaking apart artwork for sheet cutting.
    By kerrazy in forum Archives2003
    Replies: 3
    Last Post: 05-18-2003, 08:28 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •